Definitive sockets for fitting prostheses to residual limbs of amputees are made by various processes in accordance with prior art techniques. For example, numerous techniques have been developed that involve first, creating a negative mold of the residual limb, second, creating a positive mold or impression cast from the negative mold, third, modifying the positive mold to provide relief for sensitive areas of the residual limb, and fourth, forming the prosthesis socket using the modified positive mold. This technique involves numerous steps, and the negative and positive molds are typically created using Plaster-of-Paris. Some examples of this technique are embodied in U.S. Pat. No. 5,503,543, granted Apr. 2, 1996; and U.S. Pat. No. 6,991,444 granted Jan. 31, 2006, both to Laghi.
Another technique used to form prosthetic sockets is to reduce the steps in the above process by forming the socket directly on the residual limb without creating both a negative and a positive mold. This technique can be implemented in a variety of ways.
For example, U.S. Pat. No. 5,718,925, granted Feb. 15, 1998; U.S. Pat. No. 5,971,729, granted Oct. 26, 1999; U.S. Pat. No. 5,972,036, granted Oct. 26, 1999; and U.S. Pat. No. 6,416,703 granted Jul. 9, 2002, all to Kristinsson et al., and all herein incorporated by reference, all disclose a method of forming a definitive prostheses socket directly upon a residual limb. In the method, a web-like tubular braided carbon fiber sleeve that is pre-impregnated with a water curable resin is soaked in water and placed upon the residual limb. The sleeve is pressure cast in a known manner using the ICECAST ANATOMY™ system made by Össur hf of Reykjavik, Iceland, and described in U.S. Pat. No. 5,885,509, granted Mar. 23, 1999 to Kristinsson, and further modified by U.S. Pat. No. 7,105,122, granted on Sep. 12, 2006 to Karason, and U.S. Pat. No. 7,438,843, granted Oct. 21, 2008 to Asgeirsson, each of these references being herein incorporated by reference in their entirety.
U.S. Pat. No. 7,438,843 discloses another method and kit for forming a prosthetic socket directly on a residual limb. The method and kit are used to form a definitive prosthetic socket directly on a residual limb without the use of a water hardenable material. A chamber surrounding a web of braided fibers is created on the residual limb via the use of inner and outer protective sheaths. A hardenable or curable material for forming the prosthetic socket is injected into the chamber around the web. Pressure is applied around the chamber to form the definitive prosthetic socket. The same basic method may be used likewise with a positive impression cast of the residual limb.
An issue arises when forming sockets due to the residual limb deforming during the casting process. As such, the profile of the residual limb varies during casting over the normal state of the residual limb. This results in a socket that has a poor fit with the residual limb leading to painful pressure on the residual limb due to pressure points. From this poor fit, the residual limb runs the risk of forming blisters, sores and decreased blood flow.
When creating a socket, it is desired to obtain total surface bearing due to a volume match of the socket to the residual limb. If the residual limb reduces in volume, it will further drop into the socket resulting in increased distal pressure on the residual limb. If the residual limb increases in volume, it cannot fit properly into the socket, resulting in discomfort over bony prominences and excessive tension at the distal end of the residual limb.
It follows that there should be as close as possible full surface contact between the socket and the residual limb during a normal walking gait cycle. Thus, in order to successfully fit a socket to a residual limb, there must be control of the soft tissue, a minimization of pressure peaks, and a distribution of the load on the residual limb over a maximum surface area.
In many conventional casting methods, a standard suspension liner is donned on the residual limb to approximate the necessary volume of the residual limb and suspension liner. Yet, the standard suspension liner often creates too much volume for the socket and thereby leads to a poorly fitting socket. This necessitates for manual manipulation of the socket to achieve the necessary volume, and therefore adds to manufacturing time and requires substantial skill to achieve the necessary volume.
In order to assure that there is total surface bearing between the residual limb and the socket, a method and kit for casting a socket must evenly distribute the soft tissue, minimize modifications of the socket, and provide consistent results. In particular, it is undesirable to modify the cast, such as Plaster-of-Paris, for volume reduction of the socket, or manually modify a socket that has been directly cast on a residual limb. Regrettably, many of the known methods and kits for forming sockets fail to achieve these desired results.